1. Field of the Invention
The present invention relates generally to machines for folding and sealing envelopes, and more particularly to a machine for folding envelopes used for encasing floppy disks.
2. Description of the Prior Art
Envelopes used for encasing floppy disks are typically formed from a plastic backing material having a fabric liner for protecting the disk media. The envelopes are folded from precut envelope blanks by making a first transverse fold along the middle of the blank and thereafter folding a pair of edge flaps to enclose two parallel edges of the envelope. The disk is inserted through the remaining open edge which is later sealed to fully enclose the disk therein. The envelope includes various holes which provide access to the disk media. A large central hole allows the disk drive mechanism to rotate the disk, while an elongate, radial slot allows the access by the read/write head of the disk drive.
Because the envelope holds the disk in place while the disk is being read it is important that the dimensions of the jacket be maintained within very close tolerances. It is also critical that the folds be made accurately in order to assure that the folded envelope remains absolutely flat after the folds have been sealed. The task of folding these envelopes is further complicated when the envelope holes are precut in the envelope blank. The holes in such precut envelope blanks must be accurately aligned after the folding is complete.
While machines have been developed which can accurately fold disk envelopes within the close tolerances required, the prior art devices are typically slow, usually requiring at least a six to eight second cycle time to produce a folded envelope ready for disk insertion. One of the fastest of these machines is the Linear Automated Primary Folding Machine, manufactured by Seaborn Development, Inc., Campbell, Calif. The Seaborn machine includes a pair of folding stations arranged on a linear track. An envelope blank is fed into one end of the machine, folded in half over an elongate mandrel located at the first station. The mandrel is then used to advance the envelope to the second folding station. At the second folding station, the side flaps on the envelope are folded over and the envelope flaps are sealed by a heat stake mechanism. Both folding operations require that the fold lines be heated prior to actual folding. The folded envelope is then removed from the machine. The cycle time for producing a folded envelope by this machine is on the order of six to eight seconds, and the machine suffers from a number of inherent limitations which prevent the reduction of the cycle time. For example, the use of the mandrel to advance the envelope prevents introduction of a new envelope blank until a previous blank has been advanced to the output area of the machine. Moreover, the side flaps must be clamped in place for at least one to three seconds after having been heated and folded in order to assure that the folds cool and set. Such clamping time prevents the advance of the envelope from the second station which in turn prevents introducing a new envelope blank at the first station.